Marssonina blotch is an agriculturally significant disease which results in leaf spotting and premature defoliation in apples, roses, etc. The leaf spots in the early stage of Marssonina are brown or yellowish brown freckles and grow gradually, forming irregular lesions, with a yellow or green halo. Black sori are formed inside the lesions and conidiospores, when scattered from the sori by wind or rain, may settle in healthy trees and cause the disease. After infection, Marssonina sp., which is responsible for the outbreak of Marssonina leaf spot, usually has a latent period of 3˜4 weeks and then concurrently appears as a lot of conidia, causing premature defoliation in July ˜ August in Korea and thus significant damage for farmers.
Until now, the diagnosis of Marssonina blotch has been preformed with the naked eye both domestically and abroad, that is, the disease has been diagnosed just by observing the symptoms visible on the leaves. However, as stated above, because Marssonina blotch appears as a result of the concurrent generation of mass conidia after a long period of latency, not all fungicides are able to arrest the development of symptoms when applied after the appearance of visible symptoms.
In order to minimize the damage caused by Marssonina blotch, the pest must be controlled with fungicides before the outbreak of the disease. Therefore, there is a pressing need for a method providing the early diagnosis of Marssonina blotch.